To ensure cooling of some low pressure turbine casings, a cooling device is provided which involves a set of cooling tubes provided outside the casing, most often by surrounding the casing, such that air is sent towards the outer face of the casing considered. The cooling tubes are typically fed by several housings, and for example by two housings or four housings. In the case where the cooling tubes are fed by two housings, the latter are typically provided on either side of the casing considered, such that each housing feeds cooling tubes surrounding the casing considered with air on about one quarter of its side circumference. This is called herein an LPTCC (Low Pressure Turbine Clearance Control) type system. The LPTCC system may be controlled by the FADEC (Full Authority Digital Engine Control); this is called herein an active control, the system then being designated by the acronym LPTACC. When it is not controlled by the FADEC, this is called here a passive control for the LPTCC system. Its main function is to regulate the low pressure turbine clearance by modulating the air flow rate taken off from the bypass flow for cooling the low pressure turbine casing.
Cooling tubes, and in particular those of LPTCC systems, are secured via feed housings with the outer face of the casing they cool. Besides, it is desirable to ensure a proper positioning of the cooling tubes acting on the casing, in particular at the farthest places of the feed housings; to that end, it is provided in the state of the art the use of an attachment metal sheet which consists of a flat metal sheet under which collars are attached, the collars surrounding the cooling tubes, enabling the tubes to be held in position.
FIG. 1a shows a first perspective view of a cooling device 1 for a turbojet casing according to the state of the art. FIG. 1a thus shows:                a turbojet casing 2;        the cooling device 1 for the turbojet casing 2, the cooling device 1 including:                    a plurality of cooling tubes 3;            an air feed housing 4 of the plurality of cooling tubes 3;            a plurality of attachment metal sheets 5 for holding the plurality of cooling tubes 3 in position.                        
FIG. 1b shows a second perspective view of the cooling device 1 for a turbojet casing according to the state of the art. FIG. 1b shows in particular an attachment metal sheet 5 under which a plurality of collars 6 is attached, each collar 6 surrounding a cooling tube 3. Such a solution does not enable a proper positioning of the cooling device to be systematically ensured with respect to the casing. Axial and/or radial misalignments of the cooling tubes of the cooling device with respect to the casing are thus typically observed.
FIG. 2a schematically illustrates an example of proper positioning of a cooling tube 3 of the cooling device 1 for a turbojet casing, with respect to the turbojet casing 2. In this example:                the axial positioning, along an axial direction Ax, of the cooling tube is proper, the cooling tube 3 being aligned with a hook 7 of the casing 2, and        the radial positioning, along a radial direction Rad, of the cooling tube is proper, the radial distance between the cooling tube 3 and the casing 2 being controlled.        
FIG. 2b schematically illustrates a first example of improper positioning of the cooling tube 3 with respect to the turbojet casing 2, wherein the cooling tube 3 is in contact with the casing 2. FIG. 2c schematically illustrates a second example of improper positioning of the cooling tube 3 with respect to the turbojet casing 2, wherein the cooling tube 3 is this time very far from the casing 2. Finally, FIG. 2d schematically illustrates a third example of improper positioning of the cooling tube 3 with respect to the turbojet casing 2, wherein the cooling tube 3 is misaligned with respect to a hook 7 of the casing 2.